RESUMEN
The Chk2 kinase is a tumor suppressor and key component of the DNA damage checkpoint response that encompasses cell cycle arrest, apoptosis, and DNA repair. It has also been shown to have a role in replicative senescence resulting from dysfunctional telomeres. Some of these functions are at least partially exerted through activation of the p53 transcription factor. High-level expression of virally transduced Chk2 in A549 human lung carcinoma cells led to arrested proliferation, apoptosis, and senescence. These were accompanied by various molecular events, including p21(Waf1/Cip1) (p21) transcriptional induction, consistent with p53 activation. However, Chk2-dependent senescence and p21 transcriptional induction also occurred in p53-defective SK-BR-3 (breast carcinoma) and HaCaT (immortalized keratinocyte) cells. Small interfering RNA-mediated knockdown of p21 in p53-defective cells expressing Chk2 resulted in a decrease in senescent cells. These results revealed a p53-independent role for Chk2 in p21 induction and senescence that may contribute to tumor suppression and genotoxic treatment outcome.
Asunto(s)
Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Proteínas Serina-Treonina Quinasas/genética , Proteína p53 Supresora de Tumor/metabolismo , Apoptosis/fisiología , Neoplasias de la Mama , División Celular/fisiología , Línea Celular Transformada , Línea Celular Tumoral , Senescencia Celular/fisiología , Quinasa de Punto de Control 2 , Regulación Neoplásica de la Expresión Génica , Humanos , Queratinocitos/citología , Neoplasias Pulmonares , ARN Interferente Pequeño , Retroviridae/genética , Transducción GenéticaRESUMEN
A systematic characterization of the genetic alterations driving ALCLs has not been performed. By integrating massive sequencing strategies, we provide a comprehensive characterization of driver genetic alterations (somatic point mutations, copy number alterations, and gene fusions) in ALK(-) ALCLs. We identified activating mutations of JAK1 and/or STAT3 genes in â¼20% of 88 [corrected] ALK(-) ALCLs and demonstrated that 38% of systemic ALK(-) ALCLs displayed double lesions. Recurrent chimeras combining a transcription factor (NFkB2 or NCOR2) with a tyrosine kinase (ROS1 or TYK2) were also discovered in WT JAK1/STAT3 ALK(-) ALCL. All these aberrations lead to the constitutive activation of the JAK/STAT3 pathway, which was proved oncogenic. Consistently, JAK/STAT3 pathway inhibition impaired cell growth in vitro and in vivo.
Asunto(s)
Regulación Neoplásica de la Expresión Génica , Linfoma Anaplásico de Células Grandes/genética , Factor de Transcripción STAT3/metabolismo , Factor de Transcripción Activador 3/genética , Factor de Transcripción Activador 3/metabolismo , Animales , Línea Celular Tumoral , Células HEK293 , Humanos , Janus Quinasa 1/genética , Ratones , Proteínas Mutantes Quiméricas/genética , Proteínas Mutantes Quiméricas/metabolismo , FN-kappa B/genética , Fosforilación , Proteínas Proto-Oncogénicas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Factor de Transcripción STAT3/genética , Transducción de Señal , TYK2 Quinasa/genéticaRESUMEN
Rad9 functions in the DNA-damage checkpoint pathway of Saccharomyces cerevisiae. In whole-cell extracts, Rad9 is found in large, soluble complexes, which have functions in amplifying the checkpoint signal. The two main soluble forms of Rad9 complexes that are found in cells exposed to DNA-damaging treatments were purified to homogeneity. Both of these Rad9 complexes contain the Ssa1 and/or Ssa2 chaperone proteins, suggesting a function for these proteins in checkpoint regulation. Consistent with this possibility, genetic experiments indicate redundant functions for SSA1 and SSA2 in survival, G2/M-checkpoint regulation, and phosphorylation of both Rad9 and Rad53 after irradiation with ultraviolet light. Ssa1 and Ssa2 can now be considered as novel checkpoint proteins that are likely to be required for remodelling Rad9 complexes during checkpoint-pathway activation.